The present invention relates to an injector for injecting a gas contrast media into the bloodstream and more particularly to such an injector for injecting carbon dioxide into the bloodstream in a controlled manner.
Carbon dioxide injected into the blood stream can serve as a negative contrast media for angiographic procedures or as a blood displacement media for procedures such as arteriograms, angioscopy and laser therapy.
Liquid iodinated contrast is one presently used contrast media for angiography. The liquid iodinated contrast is injected into the bloodstream at a predetermined flow rate. When liquid iodinated contrast enters the bloodstream, it mixes with the blood and flows downstream. Although iodinated contrast media is generally useful and safe, it can create serious problems and even death in people with iodine allergies.
Saline is a known blood displacement media and is frequently used during laser therapy and angioscopy. Saline has limited use as it cannot be safely injected in large doses. Carbon dioxide, in contrast to saline, has superior light transmittance and thermal insulating properties.
Carbon dioxide, in contrast to known prior art contrast and displacement media, is inexpensive, non-toxic, and is readily released from the body by the normal breathing process. However, there have been problems safely and effectively using carbon dioxide as a contrast media with presently known delivery systems due, in part, to the fact that carbon dioxide is a compressible gas.
When carbon dioxide is injected into the vascular system, it compresses and expands along with the pressure wave created by the cardiac output. Blood forced into the aorta during cardiac systole moves the blood forward in the blood vessels and sets up a pressure wave which travels down the arteries. The arterial pressure rises during systole and lowers during diastole.
The flow rate of blood through the vascular system depends upon the cardiac cycle and blood pressure. The flow rate can be measured directly using known means.
When carbon dioxide is injected into the bloodstream, it forms bubbles. Carbon dioxide does not mix with the blood. For carbon dioxide to function as a viable contrast media or displacement media, it must completely displace the blood in the area of interest. If it does not, any area of blood not displaced will falsely appear to be a stenosis or lesion. The carbon dioxide must completely displace the blood in the area of interest for the entire injection period. For this displacement to occur the carbon dioxide must be injected at a pressure greater than the pressure of the blood itself. However, if the pressure differential between the injected carbon dioxide and the blood is too great a reflux or retrograde flow of carbon dioxide occurs. This reflux necessitates the injection of additional carbon dioxide and further creates safety problems due to the uncontrolled nature of the carbon dioxide flow.
Care must be taken with carbon dioxide to prevent blood clots from forming. Additionally, care must be taken to prevent any pressure spike at the initiation of the carbon dioxide injection. Additionally, care must be taken to avoid an explosive delivery which can cause patient pain. In order to avoid an explosive delivery care must be taken to establish a continuous column of carbon dioxide before an injection is commenced. Further, nitrogen and oxygen should be removed from the injector system to insure patient safety and comfort.
During the angiographic procedure it is advisable to flush the catheter, through which the carbon dioxide is introduced, with saline. Saline is injected whenever the flow of carbon dioxide is halted to avoid clotting of blood. It is important that all of the saline is evacuated from the system before carbon dioxide is injected and vice versa. If carbon dioxide is in the system while blood pressure is taken, the blood pressure wave may be dampened. If saline is in the system when carbon dioxide is injected, erratic delivery of the carbon dioxide may occur.
It is preferable to inject as little carbon dioxide as possible without sacrificing the integrity of the procedure and, it is preferable to have the carbon dioxide injected at the lowest pressure which still permits complete displacement of blood.
Accordingly, it is an object of the present invention to provide a device for introducing carbon dioxide into the bloodstream such that carbon dioxide can function as a contrast and blood displacement medium.
It is another object of the present invention to provide such a device which enables the carbon dioxide to completely displace the blood in the area of interest for the entire injection.
It is yet another object of the present invention to provide such a device which minimizes safety hazards and enhances patient comfort.
Yet a further object of the present invention is to provide such a device which minimizes problems, such as blood clots or explosive delivery.
Still a further object of the invention is to provide a mechanism for safely and efficiently delivering a saline drip in conjunction with the delivery of the carbon dioxide.
It is another object of the invention to provide an economical electro-gas connector that helps prolong the useful life of the receptacle on the injector.